The study proposes to validate a robotic surrogate - the Pre-toddler Inhalable Particulate Environmental Robotic (PIPER) sampler - for collecting personal exposures of particulate matter (PM) in a study population which is too young to have personal exposure collected accurately by existing methodologies. Exposure and dose estimation are essential to understanding the etiology of environmentally linked childhood diseases. The behavior of resuspended PM suggests that stationary general area measurements taken in homes may underestimate these exposures in young children. Additionally, peak levels of PM exposure may be important in understanding the origins of early childhood conditions such as asthma. Unfortunately the size and weight of sampling equipment limit or preclude their use for PM direct measurements of exposures in very young children, such as infants and toddlers (ages >6 to 36 months). The Pre-toddler Inhalable Particulate Environmental Robotic (PIPER Mk IV) has been developed over the last 5 years to provide a surrogate method to ascertain personal exposures to PM for children too young to have exposure measured by conventional personal sampling methodologies. PIPER provides a mobile autonomous platform on which to mount personal sampling devices. PIPER has been programmed to reproduce the pattern of a child's movement while at play on the floor, and as would a child disturbs and resuspends settled housedust. The PIPER Mk IV is the result of over 5 years of development and testing and has proven its reliability in tests in over 50 homes participating in an NIEHS funded (R01-ES014717) study. A validation study of an alternate personal sampling methodology using a robotic surrogate (PIPER) for young children's exposure to PM is proposed. The study will be carried out by mounting identical sampling systems on PIPER in side-by- side comparison with 100 children (50 boys and 50 girls) at play in their own homes. Children between >24 and 36 months of age will be recruited from participants of the existing PIPER Asthma Study and the pediatric practices participating in that study in central New Jersey. The goal of this validation study is to provide researchers with a new and novel tool for characterizing young children's exposure to environmental contaminants.